Cementing wells



an Avc; E. REISTLE, JR, ETAL GEMENTING WELLS Filed Nov. 27, 1944 M6 @INN June 3, 1947.

Patented June 3, 1947 CEMENTING WELLS Carl E. Relstle, Jr., and GeorgeE. Cannon,

Houston, Tex., assignors to Standard Oil Development Company, acorporation of Delaware Application November 27, 1944, Serial No.565,251

Claims.

The present invention is directed to a method for performingcementingoperations in bore holes and to apparatus useful in the practice of sucha method.

Much difiiculty is experienced in'attempts to cement casing in boreholes where the object is to seal off one or more formations. Thisdifliculty arises out of the fact that at the time a cementing operationis performed the wall of the bore hole is usually covered with a sheathof clay which has been deposited from the drilling mud. This sheath ofclay makes the effectuation of a tight bond between the cement and theformation difficult.

There have already been proposals and repeated attempts to overcome theaforesaid difiiculties by scraping the mud sheath off the wall of thebore hole prior to the cementing operation. Some degree of success hasbeen achieved by this expedient, but in view of the fact that during thescraping operation the bore hole is full of drilling mud or claysuspension, it is quite evident that along its entire length as they arebeing lowered into place to scrape the desired section. It isundesirable, however, to remove-the clay sheath from the major portionof the wall of the bore hole since it serves to seal off this wall. Theobjective is to remove the clay sheath from the particular portion ofthe wall which is to be cemented while preserving the clay sheath to thefullest extent possible in the-remainder of the bore hole. Of course,when the scraper only disturbs the clay sheath in its downward travel,this is not serious because the clay will redeposit. In most commondesigns, however, the scraper actually pushes the clay ahead of it untilthe scraper itself has a clay sheath over its forward surface. When thishappens, the scraper actually interferes with rather than aids thecementing operation.

According to the present invention, a cementing operation is improved bylowering into the well rotatable member carrying a, scraper in the formof circumferentially spaced longitudinal rows of substantiallyvertically aligned fingers or scrapers to a position in the welladjacent the formation which is to be cemented ofi, rotating the memberupon which the scraping elements are disposed for a period suflicient toeffect the removal of the clay sheath from the selected formation and,while still continuing the rotation, spotting the cement against saidformation. When this procedure is followed, redeposition of the claysheath on the formation is prevented and channeling of the cement iseliminated and an effective seal of cement on the formation surface isrealized.

The nature of the present invention will appear more clearly in thefollowing detailed des'cription of the accompanying drawing in whichFig. l is a side elevation of a rotatable member, such as a casingcarrying the scraping device of the present invention;

Fig. 2 is a cross section along the line II-II of Fig. 1;'

Fig. 3 is a detail of the scraping fingers;

Fig. 4 is a detailed section showing the securing means for saidfingers; and

- Fig. 5 is a vertical section of a bore hole showing the device inplace during a cementing operation.

Referring to. the drawing in detail, numeral I represents a casing whichis to be cemented in a Well and numeral 2 represents a sleeve slidablymounted upon said casing. This sleeve is provided with oppositelydisposed longitudinal slots .3 in which ride studs 4 carried by thecasing. Welded to the sleeve 2 are a plurality of channel members 5which, in the specific embodiment shown, are four in number. Eachchannel member is provided with a longitudinal row of aligned holes 6and spaced transversely from said holes a longitudinal parallel row ofrivets I in staggered relation to said holes. Each scraping unit is a U-shaped spring member '8, having at its base an eye 9 adapted to seat onthe head of the rivet I, and having at the end of each of its legs acoil spring III adapted to seat in the holes 6. From the end of eachcoil spring a spring finger I I extends outwardly. The extending fingermay assume any configuration and in the drawing is shown to be inclinedrearwardly with respect to the direction of rotation of the casing for aportion of its length and then radially from the casmg.

The purpose of the stud and sleeve arrangement is to permit the collar 2to travel longitudinally with respect to the casing as the latter isrotated. By this expedient the scraping mechanism is made eifectlve fora length considerably greater than its own length. It will beunderstood, however, that the collar 2 is not necessary to the assemblysince the channel members 5 can be welded directly to the caslng.-

In Fig. 5, is shown a. bore hole in which surface easing l2 has been setand the hole then extended to traverse a producing horizon l3. In theoperation to be described, the purpose is to cement a string of casingto the producing horizon in such a way as to seal of! the producinghorizon from the adjacent formations, the lower one, M, of which, forexample, may contain water while the next higher one, l5, may containgas. In the practice of the present invention, the casing which carriesthe scraping assembly is lowered into the bore hole until the scrapingassem bly is opposite the producing formation and preferably extendingon either side thereof. In this stage the hole is full of drilling mud.The casing carries a cementing shoe I6 at its lower end. The casing isrotated for a period, such as to minutes, and then with the casing stillrotating cement is pumped through it and caused to rise up On theoutside of the casing to a point above the producing formation. In somecases, it will be preferable to precede the charge of cement with acharge of clear water to assist in carrying away the broken up claysheath. After suflicient cement has been forced into the well to reachthe desired level, the rotation of the casing is stopped and the cementallowed to set. Thereafter a perforating device is lowered into thecasing and holes punched through the casing and cement into theproducing formation.

It will will be observed mat the scraping fingers are of such aconfiguration and so arranged that as the casingis lowered into thewell, the fingers cause a minimum of disturbance of the clay sheathabove the point in which effective scraping is desired. Furthermore, thearrangement of fingers is such that the possibility of any bridges ofclay sheath forming around the lower end of the scraper is extremelyremote. Finally, the fingers serve to center the casing so as to insurea layer of cement of substantially uniform thickness around the casing.

In the specific embodiment shown, a particular cementing operation isportrayed. It is to be understood that the invention is not limited tothis particular operation but is applicable to any cementing operation.These operations may be conducted from time to time for sealing a highpressure gas or water stratum regardless of the position thereof withrespect to the producing formation. I

The nature and objects of the present invention having been describedand illustrated, what we desire to claim is:

l. A scraping device for well casings comprising an elongated channelmember having a longitudinally aligned row of spring fingers,

2. A scraping device for a well casing comprising an elongated channelmember, a longitudinal row of retaining members on said channel memberand a spring member secured to each retaining member provided with aspring finger adapted to extend outwardly from said channel member tothereby provide a longitudinal row of spring fingers on said channelmember.

3. A scraping device for well casing comprising an elongated channelmember, a longtiudinal row of retaining members on said channel member,a longitudinal row of perforations in said channel member spaced fromand parallel to said retaining members, a springmember secured to eachretaining member having a coil portion adapted to seat in one of saidperforations and terminating in a spring finger extending outwardly fromsaid channel member.

4. A scrapingand centering device for well casing comprising a collarhaving therein a longitudinally extending slot and slidably mounted on asection of the casing, a multiplicity of outwardly extending spring armsmounted in a few circumferentially spaced longitudinal rows on saidcollar with all of the spring fingers in each row in alignment and astud mounted on the section of casing and riding in said slot wherebythe collar is secured to the casing for rotation therewith and is freeto move longitudinally relative thereto.

5. A scraping and centering device for a well using comprising a collarsecured to said casing for rotation therewith and for longitudinalmovement relative thereto and a plurality of circumferentially spacedlongitudinal rows of outwardly extending spring fingers carried by saidcollar.

CARL E. REISTLE, JR. GEORGE E. CANNON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,151,416 Black et a. Mar. 21,1939 2,374,317 Wright Apr. 24, 1945

